Patent Application
20240280317
The present disclosure relates to the compression of a gas and in particular to the recovery of compression energy from the gas.
Liquefying a gas generally requires the gas to be compressed at high pressure. This compression stage is referred to as isothermal, and is generally carried out by a succession of adiabatic compression stages during which the gas is heated. In this way, the gas is cooled between each compression stage before entering the next compression stage.
The gas is cooled in a heat exchanger.
In liquefiers, the heat recovered in this heat exchanger is either lost to the atmosphere or, for example as described in JP2005241232, used as a heat source for vaporizing liquid natural gas.
Coupling a liquefier to a liquefied natural gas plant requires the liquefier and the liquefied natural gas plant to be in the same location. In addition, this heat recovery solution severely limits the possibility of heat recovery, due in particular to the number of liquefied natural gas plant sites, the fluctuating demand for liquefied natural gas, which will have an impact on the cooling of the compressed gas between two compression stages, and the safety constraints associated with the presence of liquefied natural gas and liquid hydrogen, for example.
This disclosure aims to address at least partly these shortcomings.
To this end, the present disclosure relates to a system for recovering energy from gas compression, the system comprising an organic Rankine cycle module and an adiabatic compressor, the organic Rankine cycle module comprising a heat transfer fluid and the adiabatic compressor comprising N adiabatic gas compression stages, N being greater than or equal to 2, and, downstream of each adiabatic compression stage, two heat exchangers, a first heat exchanger configured to extract heat from the gas leaving the adiabatic compression stage and to heat the heat transfer fluid passing through the first heat exchanger, and a second heat exchanger configured to extract heat from the gas leaving the first heat exchanger to a cold source passing through the second heat exchanger.
Hereinafter, the terms “upstream” and “downstream” are defined in relation to the normal direction of gas flow in the system. Thus, a second element arranged downstream of a first element receives the gas leaving the first element.
Thanks to the organic Rankine cycle module, the heat of the compressed gas in an adiabatic compression stage is not lost to the atmosphere, without the need for direct coupling with a liquefied natural gas unit.
In a known way, an organic Rankine cycle module comprises at least one heat exchanger configured to heat the heat transfer fluid circulating in the module from a hot source external to the module, an expansion device for the heated heat transfer fluid, a condenser for cooling the heat transfer fluid and a pump for circulating the heat transfer fluid in the module. The expansion device expands the heated, pressurized heat transfer fluid and converts the energy recovered in the form of heat into mechanical energy. The expansion device is usually coupled to an energy recovery device that converts the mechanical energy recovered at the expansion device outlet into usable energy. In the present presentation, the hot source is the gas leaving a compression stage of the adiabatic compressor.
The system comprising, after each compression stage, a first exchanger configured to exchange heat between the gas leaving a compression stage and the heat transfer fluid of the organic Rankine cycle module, part of the heat generated during the adiabatic compression of the gas is recovered in the heat transfer fluid of the organic Rankine cycle module, the heated heat transfer fluid is then expanded in order to produce energy.
As a non-limiting example, the expansion device can be a turbine or a volumetric expansion device, for example a spiral-type expansion device, also known as “scroll” volumetric expansion device. In a general way, for high expansion ratios, e.g., greater than or equal to 7, a turbine is preferred, and for lower expansion ratios, a volumetric expansion device is preferred. Criteria other than expansion ratio may also be taken into consideration when choosing an expansion device.
As a non-limiting example, the expansion device can be coupled to an electrical generator to recover energy in electrical form.
It may also be possible to couple another device to the expansion device for converting energy into mechanical energy.
Coupling the organic Rankine cycle module to the first heat exchangers heat exchangers enables the flow rate of the vaporized heat transfer fluid to be increased, thereby increasing the size of the turbine. By increasing the size of the turbine, the relative clearances in the turbine are reduced and turbine performance is improved, thereby increasing energy recovery efficiency.
The electrical energy produced can be used to power components of the system itself or components outside the system, or even fed into the power grid.
As a non-limiting example, the compressor of the isothermal compression stage can be a positive displacement compressor or a centrifugal compressor.
In some embodiments, the second heat exchanger may be a gas-air exchanger.
In some embodiments, the second heat exchanger can be a gas-water exchanger.
In some embodiments, the heat transfer fluid may have a boiling temperature between a cold source inlet temperature and a gas outlet temperature in the adiabatic compression stage.
In some embodiments, the heat transfer fluid may be methanol, isobutane or ethanol.
The present disclosure also relates to a liquefier comprising a system as defined above.
The electrical energy produced can be used to power components of the liquefier itself or components outside the liquefier, or even fed into the power grid. Energy recovery can be around 2% to 5% of the power required to operate the liquefier, which is not insignificant considering the service life of a liquefier, which can be at least 20 years.
In some embodiments, the gas can be the gas to be liquefied.
In some embodiments, the liquefier can be a refrigerated liquefier comprising at least one cooling circuit and the gas is the gas of the at least one cooling circuit of the refrigerated liquefier and/or the gas to be liquefied.
In the case of a refrigerated liquefaction cycle with multiple cooling circuits, the gas compression energy recovery system can be implemented at the compression stages of at least one cooling circuit.
It is understood that the gas in the cooling circuit of the refrigerated liquefier can be a pure gas or a gas mixture. By pure gas is meant a gas comprising at least 99% of a gaseous compound.
In some embodiments, the gas to be liquefied may be hydrogen, nitrogen, helium or natural gas.
The present disclosure also relates to a method for recovering compression energy from a gas, the method comprising the following steps:
Further features and advantages of the object of the present disclosure will become apparent from the following description of embodiments, given by way of non-limiting examples, with reference to the appended figures.
Throughout the figures, common elements are identified by identical numerical by identical numerical references.
For simplicity's sake, the adiabatic compressor 14 and the heat exchanger 16 have been shown on
In the embodiment shown in
In the embodiment shown in
The energy recovery system comprises the adiabatic compressor adiabatic compressor 14 and heat exchanger 16. The energy recovery system also comprises an organic Rankine cycle module 40.
In the embodiment shown in
The organic Rankine cycle module 40 includes a heat transfer fluid 54 circulating in the module 40.
In the embodiment shown in
As a non-limiting example, the expansion device 42 may be a turbine or a volumetric expansion device.
In the embodiment shown in
As a non-limiting example, the expansion device 42 can be a turbine and the energy recovery device 44 can be an electrical generator for converting the mechanical energy recovered from the turbine into electrical energy. It is understood that the expansion device 42 of the organic Rankine cycle module 40 can be coupled to another energy recovery device 44, enabling the recovered energy to be converted into mechanical form, for example.
In the embodiment shown in
The heat transfer fluid 54 passes successively through the first heat exchangers 50A, 50B, 50C, where, by heat exchange with the gas 56 leaving the compression stages 14A, 14B, 14C, the heat transfer fluid 54 is brought to boiling point. The heat transfer fluid 54, in the form of steam, is then expanded in the expansion device 42, which is coupled to the energy recovery device 44. The steam is then condensed in condenser 46 by exchange with ambient air 60. The heat transfer fluid 54 is once again in liquid form and can once again pass through the first heat exchangers 14A, 14B, 14C.
The gas 56 leaving each adiabatic compression stage 14A, 14B, 14C passes through the first heat exchanger 50, 50B, 50C and exchanges part of the heat stored in the gas 56 during compression with the heat transfer fluid 54 circulating in the first heat exchanger 50A, 50B, 50C. The gas 56 leaving the first heat exchanger 50A, 50B, 50C then passes through the second heat exchanger 52A, 52B, 52C and exchanges the remaining stored heat with a cold source 58.
By way of non-limiting example, cold source 58 may be ambient air or water.
At the outlet of the second heat exchanger 52A, 52B, gas 56 enters the adiabatic compression stage located downstream of the second heat exchanger 52A, 52C. At the outlet of the second heat exchanger 52C downstream of the last adiabatic compression stage 14C, gas 56 is fed into the cold box via a pipe 30.
By way of a non-limiting example, heat transfer fluid 54 can be methanol. Methanol has a boiling temperature at approximately 1 bar equal to 338 K (Kelvin) and the cold source 58 can be ambient air estimated at 300 K.
For simplicity of representation,
As a non-limiting example, the gas temperature at the outlet of the adiabatic compression stage is limited to 400 K. Also, the boiling temperature of the heat transfer fluid 54 is between the temperature of the cold source 58 entering the second heat exchanger 52A, 52B, 52C and the temperature of the gas leaving the adiabatic compression stage 14A, 14B, 14C.
Thus, in an ideal example, the hydrogen entering the first adiabatic compression stage 14A has an ambient temperature of around 300 K (item 1 in
The compression energy recovery system can also be implemented in a refrigerated liquefaction cycle.
Refrigerated liquefaction cycles are well known to the state of the art and implement circuits for cooling/refrigerating the gas to be liquefied by using another gas or gas mixture maintained at low temperature by a refrigeration cycle which comprises compression stages specific to this gas or gas mixture and expansion stages, this other gas or gas mixture being used as refrigerant for the main liquefaction circuit. The nature of the gases or gas mixtures used as refrigerant gases in such cycles can be distinct from the nature of the gas to be liquefied in the main liquefaction circuit.
It is therefore understood that in the case of a refrigerated liquefaction cycle, the compression energy recovery system can be implemented at the compression stages specific to the refrigerated liquefaction cycle's cooling circuit.
In the case of a refrigerated liquefaction cycle with multiple cooling circuits, the gas compression energy recovery system can be implemented at the compression stages of one or more cooling circuits.
The method 100 for recovering gas compression energy 56 will be described with reference to Figures to 4.
Method 100 comprises:
In the embodiment shown in
The method 100 includes a step 110 of using the heat extracted in the first heat exchanger 50A, 50B, 50C to produce energy in the organic Rankine cycle module 40.
Although the present disclosure has been described with reference to a specific example embodiment, it is obvious that various modifications and changes can be made to these examples without departing from the general scope of the invention as defined by the claims. Furthermore, individual features of the various embodiments mentioned can be combined in additional embodiments. Consequently, the description and drawings are to be considered in an illustrative rather than a restrictive sense.
| Number | Date | Country | Kind |
|---|---|---|---|
| FR2106353 | Jun 2021 | FR | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/FR2022/051117 | 6/13/2022 | WO |
